The creature, nicknamed "Woman X" for the time being, could have lived as recently as 30,000 years ago and appears only distantly related to modern humans or Neanderthals, the researchers reported.

"It really just looked like something we had never seen before," Johannes Krause of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, told a telephone briefing, according to Reuters.

After exhaustive tests on DNA extracted from the fragment, scientists say a previously unknown type of human, neither Homo sapiens nor Neanderthal, lived in Siberia at this time.

It raises the intriguing possibility that three species of human were living alongside one another, perhaps for thousands of years.

Nothing is known of how they interacted or whether they interbred but it is clear that only one of the three species survived: anatomically modern humans.

Scientists have no other physical remains of the mysterious hominin. They don't know its gender, but the size of the bone suggests it belonged to a child aged seven or eight. Carbon dating of the sediments surrounding it indicates he or she lived between 30,000 and 48,000 years ago, Hamilton Spectator reported.

According to Dallas Morning News, the pinkie bone, from a child age 7 to 9 but of unknown gender, was found in the Denisova Cave in southern Siberia. The cave shows signs of being occupied by humans and their relatives periodically for at least 125,000 years.

The new species shared an ancestor with both modern humans and Neanderthals about 1 million years ago, based on the DNA sequences, according to the team led by anthropologists Johannes Krause and Svante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.